LOL, I don't understand how people can repair your keyboard through Intenet, even withhout inspecting it. Big respect, lol I repair Yamaha keyboards, and I cannot confirm what people say. Obviously it MIGHT be a problem with connector, with cable, or with power supply, but there are not all reasons why keyboard turns off. Even not official power supplies (even with not appropriate voltage) are quite fine in most cases, by the way.

Only servicing might help and remove the fault. As someone said - "an advice is worth exactly what you paid for it".-LINK-